The optical modulation device includes plural interactive parts which interact with a light-wave and modulate the light-wave so as to support multi-level modulation or polarization multiplexing modulation. An electrical signal for modulation of the light-wave is supplied to each of the interactive parts through electrical line that is provided to each of the interactive parts. As described above, in the case where the optical modulation device includes the plural interactive parts, it is demanded to make electrical lengths of the electrical lines, which extend to the interactive parts, even, and to keep the same electrical loss between the electrical lines provided to the respective interactive parts so as to make electrical signal states input to the respective interactive parts coincide with each other.
For example, an optical modulation device described in Patent Literature No. 1 includes an optical waveguide element having plural interactive parts (modulation units) and plural electrical lines configured to supply an electrical signal to the respective interactive parts. In addition, propagation loss is reduced by increasing the thickness of a line which has a high loss, among the electrical lines, thereby keeping the same loss between the respective electrical lines.